A wiring board including an insulating substrate, and an external electrode and a dissipating metal layer on the main surface of the insulating substrate to be bonded to a module substrate has been known thus far. The wiring board is bonded to the module substrate with solder interposed between the external electrode and the dissipating metal layer (for example, see Japanese Patent Application Publication No. 2005-191203).
Such a wiring board may have an electrode having a slit to release gas generated if bonded with solder.